Embodiments in accordance with the invention relate to wireless data communication, and in particular to a multi-frequency band receiver and to a method of receiving signals using a multi-frequency band receiver.
Feasible input architectures, or front-end architectures (front end: input-side component), for Global Navigation Satellite System receivers (GNSS receivers) are designed to only receive one frequency band in each case. However, for high-precision GNSS receivers, it is precisely the reception of several frequency bands that is of vital importance, since it is only in this manner that inaccuracies due to ionospheric effects, for example, may be subtracted out.
With input stages, or front ends, for GNSS multi-frequency band receivers, the individual frequency bands are currently processed separately. Thus, an individual input stage or an individual front end may be used for each frequency band. This often also entails that a specific baseband stage and a specific oscillator stage may be used for each frequency band. Consequently, a large number of components and, therefore, a large amount of space may be used. Likewise, the current consumption of the input stages of the different frequency bands add up considerably, which is often critical, for example, for mobile satellite navigation receivers, but also in many other fields.
A single input stage that is sufficiently broadband for several frequency bands, or a sufficiently broadband front end, is very costly and may consume a large amount of current due to the high bandwidth. However, the high bandwidth is useful since the frequency bands are often spaced far apart. For example, in the “Galileo” GNSS, the E1 band is about 380 MHz above the E5a/b band. A bandwidth of about 430 MHz would be useful.
Processing of several frequency bands in only one broadband input stage not only strongly increases the current consumption, but the requirements placed upon the various components are also very high, since the components are designed for a broad frequency range.
Other approaches utilize an input architecture, or front-end architecture, that may be switched to other frequency bands as desired—however, this does not provide any advantage for ionosphere correction, for example, since for this purpose, at least two frequency bands may be available at the same time. Thus, for any applications requiring real-time information from several frequency bands, a switchable input architecture processing the various frequency bands one after the other is not useful.
US 2007/0096980 A1 shows an RF receiver for GNSS signals, consisting of a single chip and a small number of external components and having a number of independent signal paths, each path having a separate IF stage and baseband down converters. Each signal path is matched to a specific IF band by selection of an external IF filter. The local oscillator frequency lies in the center of all of the receiver's frequency bands to be processed.
In addition, CA 2542702 A1 shows a multi-band receiver for utilization in satellite distance systems.
WO 2006/038050 A1 shows a two-frequency receiver for signals having extensive spectra, a receive signal being received which comprises a first signal having a first frequency center and a second signal having a second frequency center. Processing is effected in one path.
In addition, U.S. Pat. No. 6,038,248 shows a method and a device for receiving and converting a signal having an extensive spectrum. Processing again is effected in one path.
WO 2008/000383 A1 shows a signal conditioner for processing a receive signal having a first useful frequency band and a second useful frequency band. Processing of the frequency bands is effected in one path.
In addition, WO 01/39364 A1 shows a multi-band receiver. Again, processing of the signals is effected only in one path.
Moreover, “Pizzarulli, A.; et al.: Reconfigurable and simultaneous dual band Galileo/GPS front-end receiver in 0.13 μm RFCMOS” shows a reconfigurable and simultaneous dual-band Galileo/GPS front-end receiver that was realized in 0.13 μm RFCMOS (Radio Frequency Complementary Metal Oxide Semiconductor) technology. The front end uses only one fixed PLL and a VCO having a superheterodyn architecture for down converting two RF (radio-frequency) signals to two IF (intermediate-frequency) signals within the range from 50 MHz to 150 MHz. L1 and E1 signals are converted directly within a channel with one mixer. L2, E6, E5, E5a, E5b signals are down converted by means of a double-stage (2 mixers) conversion.
DE 10 2006 029 482 A1 shows a receiver and a method of receiving a first useful frequency band and a second useful frequency band, the useful frequency bands being spaced apart from each other, and comprises a bandpass filter means for filtering one or more receive signals, said bandpass filter means being configured to provide a combination signal having the first useful frequency band and the second useful frequency band, or a first bandpass filter signal having the first useful frequency band, and a second bandpass filter signal having the second useful frequency band. The receiver further comprises a mixer means for converting the combination signal or the first bandpass filter signal and the second bandpass filter signal using a local oscillator signal whose frequency is selected such that the first useful frequency band and the second useful frequency band are, at least in part, mutual mirror bands with regard to the frequency of the local oscillator signal, so as to obtain a first intermediate-frequency signal and a second intermediate-frequency signal. In addition, the receiver has an intermediate-frequency filter means for filtering the first intermediate-frequency signal and the second intermediate-frequency signal so as to obtain a first filtered intermediate-frequency signal and a second filtered intermediate-frequency signal.
In addition, WO 2006/085255 A1 shows a receiver for simultaneously receiving various radio-frequency signals in accordance with various standards, said receiver comprising a first frequency conversion stage for converting the radio-frequency signal to a first intermediate-frequency signal, and comprising a second frequency conversion stage for converting the first intermediate-frequency signal to a second intermediate-frequency signal, and comprising a processing stage for retrieving first information from the first intermediate-frequency signal and second information from the second intermediate-frequency signal.